Download or read book Gas Hydrate Reservoirs and Associated Methane Migration Mechanisms on Continental Margins written by Li Wei (Ph. D. in earth sciences) and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Natural gas hydrate has been studied for its natural gas storage capacity, its significant role in global carbon cycles and its possible link to continental margin submarine landslides. However, the role of gas hydrate systems in broad global processes is still not well understood due to the large uncertainties in the estimate of global distribution and concentration of gas hydrate. For a given marine geosystems, the location and volume of gas hydrate accumulations heavily rely on the methane migration mechanisms, which are important links between the gas source and gas hydrate reservoir in natural gas hydrate systems. Numerical models are a great tool to explore methane migration mechanisms for natural gas hydrate accumulations by providing a framework that combines the geophysical, geochemical, geobiological, and geological measurements. The goal of this dissertation is to apply methane transport-reaction models to better understand the mechanisms and key factors that control gas hydrate accumulations in different marine settings. In Chapter 2, I focus on gas hydrate formation in thin, isolated, coarse- grained layers and in surrounding fine-grained hydrate-free zones. I use the available geophysical logging data measured in Walker Ridge 313 (WR 313) Hole H and Hole G in the northern Gulf of Mexico, combined with advection- diffusion-reaction model to explore the hydrate formation mechanisms in the 3 m-thick Red Sand and the 4 m-thick Purple Sand. The advection-diffusion- reaction model involves aqueous methane diffusion, methane transport with water advection, and methane generation. I confirm that a short-range methane diffusion mechanism is able to explain the hydrate accumulations in thin layers and the hydrate-free zones in the surrounding muds. I show the key parameters that control the total amount of methane and hydrate formation within coarse- grained layers as well as the thickness of hydrate-free zones in the surrounding fine-grained muds. This work is published in Geochemistry, Geophysics, Geosystems, titled Factors Controlling Short-Range Methane Migration of Gas Hydrate Accumulations in Thin Coarse-Grained Layers. In Chapter 3, I describe in detail the time-dependent calculation of dissolved methane concentration and gas hydrate content in the advection- diffusion-reaction model. The partial differential equations for the mass balance of sedimentary organic carbon, methane, and hydrate are solved in terms of material derivatives. The material derivatives for each component are then solved applying a semi-Lagrangian finite difference method combined with a fractional step method, which is an effective mathematical method for solving advection problems. In addition, I show the key assumptions made in the development of the methane hydrate formation model in this work. In Chapter 4, I focus on high saturations (79-93% in pore volume) of hydrate formation in thick, coarse-grained sediments at Green Canyon 955 (GC 955) in the northern Gulf of Mexico. I use 1D and 2D numerical models and compare the predicted gas hydrate formation in coarse-grained layers with different mechanisms. I show that short-range methane diffusion and upward water advection are not enough to form high saturations of hydrate in the GC 955 reservoir, but the free gas flow is required to form high saturations of hydrate at GC 955. This work has been accepted to the special volume of American Association of Petroleum Geologists (AAPG) Bulletin, titled Methane Migration Mechanisms for The GC 955 Gas Hydrate Reservoir, Northern Gulf of Mexico. In Chapter 5, I focus on the gas hydrate system on the Hikurangi Margin, offshore New Zealand, where the reservoir is cm-thick, coarse-grained silts bounded with fine-grained muds that contain no hydrate. I show the estimation of the base of gas hydrate stability zone (GHSZ) applying temperature measurements from coring and logging and the hydrate phase boundaries calculated from Sloan and Koh (2008) and Tishchenko et al., 2005. The estimated depth to the base of GHSZ are compared to that applied in Pecher et al. (2018), Screaton et al. (2019), and Sultan (2019). In addition, I apply previously developed 1D microbial methanogenesis advection-diffusion- reaction model to test methane migration mechanisms to form hydrate reservoir at Hikurangi Margin. In Chapter 6, I summarize the effects of different methane transport mechanisms that are short-range diffusion, upward water advection, and free gas flow on gas hydrate accumulations in heterogeneous marine sediments. I conclude that hydrate distribution and volume in marine settings depends heavily on the methane migration mechanisms, but it is also controlled by the amount of methane supply and sediment heterogeneity.

Download or read book World Atlas of Submarine Gas Hydrates in Continental Margins written by Jürgen Mienert and published by Springer Nature. This book was released on 2022-01-01 with total page 515 pages. Available in PDF, EPUB and Kindle. Book excerpt: This world atlas presents a comprehensive overview of the gas-hydrate systems of our planet with contributions from esteemed international researchers from academia, governmental institutions and hydrocarbon industries. The book illustrates, describes and discusses gas hydrate systems, their geophysical evidence and their future prospects for climate change and continental margin geohazards from passive to active margins. This includes passive volcanic to non-volcanic margins including glaciated and non-glaciated margins from high to low latitudes. Shallow submarine gas hydrates allow a glimpse into the past from the Last Glacial Maximum (LGM) to modern environmental conditions to predict potential changes in future stability conditions while deep submarine gas hydrates remained more stable. This demonstrates their potential for rapid reactions for some gas hydrate provinces to a warming world, as well as helping to identify future prospects for environmental research. Three-dimensional and high-resolution seismic imaging technologies provide new insights into fluid flow systems in continental margins, enabling the identification of gas and gas escape routes to the seabed within gas hydrate environments, where seabed habitats may flourish. The volume contains a method section detailing the seismic imaging and logging while drilling techniques used to characterize gas hydrates and related dynamic processes in the sub seabed. This book is unique, as it goes well beyond the geophysical monograph series of natural gas hydrates and textbooks on marine geophysics. It also emphasizes the potential for gas hydrate research across a variety of disciplines. Observations of bottom simulating reflectors (BSRs) in 2D and 3D seismic reflection data combined with velocity analysis, electromagnetic investigations and gas-hydrate stability zone (GHSZ) modelling, provide the necessary insights for academic interests and hydrocarbon industries to understand the potential extent and volume of gas hydrates in a wide range of tectonic settings of continental margins. Gas hydrates control the largest and most dynamic reservoir of global carbon. Especially 4D, 3D seismic but also 2D seismic data provide compelling sub-seabed images of their dynamical behavior. Sub-seabed imaging techniques increase our understanding of the controlling mechanisms for the distribution and migration of gas before it enters the gas-hydrate stability zone. As methane hydrate stability depends mainly on pressure, temperature, gas composition and pore water chemistry, gas hydrates are usually found in ocean margin settings where water depth is more than 300 m and gas migrates upward from deeper geological formations. This highly dynamic environment may precondition the stability of continental slopes as evidenced by geohazards and gas expelled from the sea floor. This book provides new insights into variations in the character and existence of gas hydrates and BSRs in various geological environments, as well as their dynamics. The potentially dynamic behavior of this natural carbon system in a warming world, its current and future impacts on a variety of Earth environments can now be adequately evaluated by using the information provided in the world atlas. This book is relevant for students, researchers, governmental agencies and oil and gas professionals. Some familiarity with seismic data and some basic understanding of geology and tectonics are recommended.

Download or read book Gas Hydrate Appearance Accumulation Exploration and Exploitation in Continental Margins written by Pibo Su and published by Frontiers Media SA. This book was released on 2023-06-02 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gas hydrate appearance accumulation exploration and exploitation in continental margins volume 2 written by Pibo Su and published by Frontiers Media SA. This book was released on 2023-02-13 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gas Hydrates written by J.-P. Henriet and published by Geological Society of London. This book was released on 1998 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: From a geological perspective, gas hydrates are an important feature of the shallow geosphere. If current estimates are correct, gas hydrates contain more potential fossil fuel energy than is present in conventional oil, gas and coal deposits, although it is uncertain how much of this can be exploited. They are also geological agents that affect the physical, geophysical and geochemical properties of sediments. Oceanic gas hydrates are increasingly recognized as a major potential hazard for the stability of offshore structures in various deep-water hydrocarbon provinces. The possibility also exists that a large release of methane from gas hydrates may have a significant impact on the radiative properties of the atmosphere and thus influence global climate: past, present and future. Following an introduction and overviews, this book covers analysis and modelling of hydrate formation; exploration strategy and reservoir evaluation; regional case studies; relevance to margin stability and climate change. Hydrate research informatiloln is presented from the USA, Russia, South Asia and the European Union.

Download or read book Gas Hydrate written by Umberta Tinivella and published by MDPI. This book was released on 2019-11-28 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Special Issue reports research spanning from the analysis of indirect data, modeling, and laboratory and geological data confirming the intrinsic multidisciplinarity of gas hydrate studies. The study areas are (1) Arctic, (2) Brazil, (3) Chile, and (4) the Mediterranean region. The results furnished an important tessera of the knowledge about the relationship of a gas hydrate system with other complex natural phenomena such as climate change, slope stability and earthquakes, and human activities.

Download or read book The Interdependence of Lithologic Heterogeneity and Methane Migration on Gas Hydrate Formation in Marine Sediments written by Michael Anthony Nole and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Despite the ubiquity of methane hydrate in the pore space of shallow marine sediments worldwide, the processes governing the transport of methane from source to reservoir are still poorly understood. Methane migration mechanisms constitute important links in the evolution of a natural gas hydrate system because they control how gas hydrate distributes in sediment pore space as well as the quantities in which gas hydrate forms. Without a thorough understanding of methane migration, it is impossible to accurately predict how a methane source interacts with a reservoir, which makes it very difficult to reliably predict where hydrate will form in a given environment. When trying to understand a gas hydrate system as a potential natural gas prospect, as a geohazard, or as an agent of global climate change, it is essential to accurately characterize the distribution and volume of hydrate present. Thus, methane migration mechanisms must be properly understood if a hydrate system is to be evaluated for any of these purposes. The work presented here develops 3D, multiphase, multicomponent fluid transport simulation software to investigate the impact of three different methane migration mechanisms on the transport dynamics and distribution of gas hydrate in marine geosystems: diffusion, short-range advection, and methane recycling. I find that the expressions of gas hydrate systems in nature are sensitive to small-scale heterogeneities in sediment lithology and capillary effects. Properties of a hydrate-bearing unit including pore size distribution, unit thickness, dip, and proximity to other layers in multilayered systems all contribute to preferential flux of methane toward and within certain hydrate-bearing sediment strata, which impact the distribution of hydrate throughout these units. When sediments are overpressured, permeability contrasts can focus methane-charged fluids along high permeability pathways and precipitate hydrate through short-range advection. Capillary phenomena can produce a region near the base of the hydrate stability zone where hydrate, water, and free gas coexist over a range of pressures and temperatures, which can drive recycling of free gas derived from dissociated hydrate back into the hydrate stability zone

Download or read book Numerical Investigations of the Fluid Flows at Deep Oceanic and Arctic Permafrost Associated Gas Hydrate Deposits written by Jennifer Mary Frederick and published by . This book was released on 2013 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Methane hydrate is an ice-like solid which sequesters large quantities of methane gas within its crystal structure. The source of methane is typically derived from organic matter broken down by thermogenic or biogenic activity. Methane hydrate (or more simply, hydrate) is found around the globe within marine sediments along most continental margins where thermodynamic conditions and methane gas (in excess of local solubility) permit its formation. Hydrate deposits are quite possibly the largest reservoir of fossil fuel on Earth, however, their formation and evolution in response to changing thermodynamic conditions, such as global warming, are poorly understood. Upward fluid flow (relative to the seafloor) is thought to be important for the formation of methane hydrate deposits, which are typically found beneath topographic features on the seafloor. However, one-dimensional models predict downward flow relative to the seafloor in compacting marine sediments. The presence of upward flow in a passive margin setting can be explained by fluid focusing beneath topography when sediments have anisotropic permeability due to sediment bedding layers. Even small slopes (10 degrees) in bedding planes produce upward fluid velocity, with focusing becoming more effective as slopes increase. Additionally, focusing causes high excess pore pressure to develop below topographic highs, promoting high-angle fracturing at the ridge axis. Magnitudes of upward pore fluid velocity are much larger in fractured zones, particularly when the surrounding sediment matrix is anisotropic in permeability. Enhanced flow of methane-bearing fluids from depth provides a simple explanation for preferential accumulation of hydrate under topographic highs. Models of fluid flow at large hydrate provinces can be constrained by measurements of naturally-occurring radioactive tracers. Concentrations of cosmogenic iodine, 129-I, in the pore fluid of marine sediments often indicate that the pore fluid is much older than the host sediment. Old pore fluid age may reflect complex flow patterns, such a fluid focusing, which can cause significant lateral migration as well as regions where downward flow reverses direction and returns toward the seafloor. Longer pathlines can produce pore fluid ages much older than that expected with a one-dimensional compaction model. For steady-state models with geometry representative of Blake Ridge (USA), a well-studied hydrate province, pore fluid ages beneath regions of topography and within fractured zones can be up to 70 Ma old. Results suggest that the measurements of 129-I/127-I reflect a mixture of new and old pore fluid. However, old pore fluid need not originate at great depths. Methane within pore fluids can travel laterally several kilometers, implying an extensive source region around the deposit. Iodine age measurements support the existence of fluid focusing beneath regions of seafloor topography at Blake Ridge, and suggest that the methane source at Blake Ridge is likely shallow. The response of methane hydrate reservoirs to warming is poorly understood. The great depths may protect deep oceanic hydrates from climate change for the time being because transfer of heat by conduction is slow, but warming will eventually be felt albeit in the far future. On the other hand, unique permafrost-associated methane hydrate deposits exist at shallow depths within the sediments of the circum-Arctic continental shelves. Arctic hydrates are thought to be a relict of cold glacial periods, aggrading when sea levels are much lower and shelf sediments are exposed to freezing air temperatures. During interglacial periods, rising sea levels flood the shelf, bringing dramatic warming to the permafrost- and hydrate-bearing sediments. Permafrost-associated methane hydrate deposits have been responding to warming since the last glacial maximum ~18 kaBP as a consequence of these natural glacial cycles. This `experiment, ' set into motion by nature itself, allows us a unique opportunity to study the response of methane hydrate deposits to warming. Gas hydrate stability in the Arctic and the permeability of the shelf sediments to gas migration is thought to be closely linked with relict submarine permafrost. Submarine permafrost extent depends on several environmental factors, such as the shelf lithology, sea level variations, mean annual air temperature, ocean bottom water temperature, geothermal heat flux, groundwater hydrology, and the salinity of the pore water. Effects of submarine groundwater discharge, which introduces fresh terrestrial groundwater off-shore, can freshen deep marine sediments and is an important control on the freezing point depression of ice and methane hydrate. While several thermal modeling studies suggest the permafrost layer should still be largely intact near-shore, many recent field studies have reported elevated methane levels in Arctic coastal waters. The permafrost layer is thought to create an impermeable barrier to fluid and gas flow, however, talik formation (unfrozen regions within otherwise continuous permafrost) below paleo-river channels can create permeable pathways for gas migration from depth. This is the first study of its kind to make predictions of the methane gas flux to the water column from the Arctic shelf sediments using a 2D multi-phase fluid flow model. Model results show that the dissociation of methane hydrate deposits through taliks can supersaturate the overlying water column at present-day relative to equilibrium with the atmosphere when taliks are large (> 1 km width) or hydrate saturation is high within hydrate layers (> 50% pore volume). Supersaturated waters likely drive a net flux of methane into the atmosphere, a potent greenhouse gas. Effects of anthropogenic global warming will certainly increase gas venting rates if ocean bottom water temperatures increase, but likely won't have immediately observable impacts due to the long response times.

Download or read book Natural Gas Hydrate written by M.D. Max and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 665 pages. Available in PDF, EPUB and Kindle. Book excerpt: 1. THE BEGINNINGS OF HYDRATE RESEARCH Until very recently, our understanding of hydrate in the natural environment and its impact on seafloor stability, its importance as a sequester of methane, and its potential as an important mechanism in the Earth's climate change system, was masked by our lack of appreciation of the vastness of the hydrate resource. Only a few publications on naturally occurring hydrate existed prior to 1975. The first published reference to oceanic gas hydrate (Bryan and Markl, 1966) and the first publication in the scientific literature (Stoll, et a1., 1971) show how recently it has been since the topic of naturally occurring hydrate has been raised. Recently, however, the number of hydrate publications has increased substantially, reflecting increased research into hydrate topics and the initiation of funding to support the researchers. Awareness of the existence of naturally occurring gas hydrate now has spread beyond the few scientific enthusiasts who pursued knowledge about the elusive hydrate because of simple interest and lurking suspicions that hydrate would prove to be an important topic. The first national conference on gas hydrate in the U.S. was held as recently as April, 1991 at the U.S. National Center of the U.s. Geological Survey in Reston Virginia (Max et al., 1991). The meeting was co-hosted by the U.s. Geological Survey, the Naval Research Laboratory, and the U.S.

Download or read book Unconventional Petroleum Geology written by Caineng Zou and published by Elsevier. This book was released on 2017-03-10 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unconventional Petroleum Geology, Second Edition presents the latest research results of global conventional and unconventional petroleum exploration and production. The first part covers the basics of unconventional petroleum geology, its introduction, concept of unconventional petroleum geology, unconventional oil and gas reservoirs, and the origin and distribution of unconventional oil and gas. The second part is focused on unconventional petroleum development technologies, including a series of technologies on resource assessment, lab analysis, geophysical interpretation, and drilling and completion. The third and final section features case studies of unconventional hydrocarbon resources, including tight oil and gas, shale oil and gas, coal bed methane, heavy oil, gas hydrates, and oil and gas in volcanic and metamorphic rocks. Provides an up-to-date, systematic, and comprehensive overview of all unconventional hydrocarbons Reorganizes and updates more than half of the first edition content, including four new chapters Includes a glossary on unconventional petroleum types, including tight-sandstone oil and gas, coal-bed gas, shale gas, oil and gas in fissure-cave-type carbonate rocks, in volcanic reservoirs, and in metamorphic rocks, heavy crude oil and natural bitumen, and gas hydrates Presents new theories, new methods, new technologies, and new management methods, helping to meet the demands of technology development and production requirements in unconventional plays

Download or read book Development of Geophysical Methods to Characterize Methane Hydrate Reservoirs on a Laboratory Scale written by Mike Priegnitz and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas hydrates are crystalline solids composed of water and gas molecules. They are stable at elevated pressure and low temperatures. Therefore, natural gas hydrate deposits occur at continental margins, permafrost areas, deep lakes, and deep inland seas. During hydrate formation, the water molecules rearrange to form cavities which host gas molecules. Due to the high pressure during hydrate formation, significant amounts of gas can be stored in hydrate structures. The water-gas ratio hereby can reach up to 1:172 at 0°C and atmospheric pressure. Natural gas hydrates predominantly contain methane. Because methane constitutes both a fuel and a greenhouse gas, gas hydrates are a potential energy resource as well as a potential source for greenhouse gas. This study investigates the physical properties of methane hydrate bearing sediments on a laboratory scale. To do so, an electrical resistivity tomography (ERT) array was developed and mounted in a large reservoir simulator (LARS). For the first time, the ERT array was applied to hydrate saturated sediment samples under controlled temperature, pressure, and hydrate saturation conditions on a laboratory scale. Typically, the pore space of (marine) sediments is filled with electrically well conductive brine. Because hydrates constitute an electrical isolator, significant contrasts regarding the electrical properties of the pore space emerge during hydrate formation and dissociation. Frequent measurements during hydrate formation experiments permit the recordings of the spatial resistivity distribution inside LARS. Those data sets are used as input for a new data processing routine which transfers the spatial resistivity distribution into the spatial distribution of hydrate saturation. Thus, the changes of local hydrate saturation can be monitored with respect to space and time. This study shows that the developed tomography yielded good data quality and resolved even small amounts of hydrate saturation inside the sediment sample. The conversion algorithm transforming the spatial resistivity distribution into local hydrate saturation values yielded the best results using the Archie-var-phi relation. This approach considers the increasing hydrate phase as part of the sediment frame, metaphorically reducing the sample's porosity. In addition, the tomographical measurements showed that fast lab based hydrate formation processes cause small crystallites to form which tend to recrystallize. Furthermore, hydrate dissociation experiments via depressurization were conducted in order to mimic the 2007/2008 Mallik field trial. It was observed that some patterns in gas and water flow could be reproduced, even though some setup related limitations arose. In two additional long-term experiments the feasibility and performance of CO2-CH4 hydrate exchange reactions were studied in LARS. The tomographical system was used to monitor the spatial hydrate distribution during the hydrate formation stage. During the subsequent CO2 injection, the tomographical array allowed to follow the CO2 migration front inside the sediment sample and helped to identify the CO2 breakthrough.

Download or read book Chemical and Biogeochemical Processes at Methane and Other Cold Seeps written by Davide Oppo and published by Frontiers Media SA. This book was released on 2023-10-31 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Methane is a strong climate-active gas, the concentration of which is rapidly increasing in the atmosphere. Vast methane reservoirs are hosted in seafloor sediments, both dissolved in pore fluids and trapped in gas hydrate. Cold seeps discharge significant amounts of this methane into the ocean. The rate of seabed methane discharge could be orders of magnitude higher than current estimates, creating considerable uncertainty. The extent of methane transfer from the seafloor to the water column and ultimately to the atmosphere is also uncertain. The seepage of methane and other hydrocarbons drives complex biogeochemical processes in marine sediments and the overlying water column. Seeps support chemosynthesis-based communities and impact the chemistry of the water column. Seeps may also play a critical role in ocean acidification and deoxygenation and can be geohazards, as well as a potential energy resource. Unraveling the complex and dynamic interactions and processes at marine seeps is crucial for our understanding of element cycling in the geo- and hydrosphere.

Download or read book Geological Controls for Gas Hydrates and Unconventionals written by Sanjeev Rajput and published by Elsevier. This book was released on 2016-05-17 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geological Controls for Gas Hydrate Formations and Unconventionals tells the story of unconventional hydrocarbon resources, especially gas hydrates, tight gas, shale gas, liquid- rich shale, and shale oil, to future generations. It presents the most current research in unconventionals, covering structural constituents of continental margins and their role in generating hydrocarbons. Additionally, this book answers basic questions regarding quantifications and characterizations, distributions, modes of occurrence, physical and chemical properties, and more - in essence, all the information that is necessary to improve the models for precision prediction of the enigma of gas hydrates and other unconventionals. Blending geology, geophysics, geomechanics, petrophysics, and reservoir engineering, it explains in simple language the scientific concepts that are necessary to develop geological and reservoir models for unconventionals. Serving as a focal point for geoscientists and engineers conducting research that focuses on reservoir characteristics of unconventionals, Geological Controls for Gas Hydrate Formations and Unconventionals is a useful resource for a variety of other specialiststies including physicists, geochemists, exploration geologists, and petroleum and reservoir engineers. It details the key factors for successful exploration and development of unconventional reservoirs including discovery, data evaluation, full-field development, production, and abandonment, along with a vivid description ofn the worldwide occurrence of unconventional hydrocarbons.

Download or read book Development of Geophysical Methods to Characterize Methane Hydrate Reservoirs on a Laboratory Scale written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas hydrates are crystalline solids composed of water and gas molecules. They are stable at elevated pressure and low temperatures. Therefore, natural gas hydrate deposits occur at continental margins, permafrost areas, deep lakes, and deep inland seas. During hydrate formation, the water molecules rearrange to form cavities which host gas molecules. Due to the high pressure during hydrate formation, significant amounts of gas can be stored in hydrate structures. The water-gas ratio hereby can reach up to 1:172 at 0°C and atmospheric pressure. Natural gas hydrates predominantly contain methane. Because methane constitutes both a fuel and a greenhouse gas, gas hydrates are a potential energy resource as well as a potential source for greenhouse gas. This study investigates the physical properties of methane hydrate bearing sediments on a laboratory scale. To do so, an electrical resistivity tomography (ERT) array was developed and mounted in a large reservoir simulator (LARS). For the first time, the ERT array was applied to hydrate saturated sediment samples under controlled temperature, pressure, and hydrate saturation conditions on a laboratory scale. Typically, the pore space of (marine) sediments is filled with electrically well conductive brine. Because hydrates constitute an electrical isolator, significant contrasts regarding the electrical properties of the pore space emerge during hydrate formation and dissociation. Frequent measurements during hydrate formation experiments permit the recordings of the spatial resistivity distribution inside LARS. Those data sets are used as input for a new data processing routine which transfers the spatial resistivity distribution into the spatial distribution of hydrate saturation. Thus, the changes of local hydrate saturation can be monitored with respect to space and time. This study shows that the developed tomography yielded good data quality and resolved even small amounts of hydrate saturation inside the sediment sample. The conversion algorithm transforming the spatial resistivity distribution into local hydrate saturation values yielded the best results using the Archie-var-phi relation. This approach considers the increasing hydrate phase as part of the sediment frame, metaphorically reducing the sample's porosity. In addition, the tomographical measurements showed that fast lab based hydrate formation processes cause small crystallites to form which tend to recrystallize. Furthermore, hydrate dissociation experiments via depressurization were conducted in order to mimic the 2007/2008 Mallik field trial. It was observed that some patterns in gas and water flow could be reproduced, even though some setup related limitations arose. In two additional long-term experiments the feasibility and performance of CO2-CH4 hydrate exchange reactions were studied in LARS. The tomographical system was used to monitor the spatial hydrate distribution during the hydrate formation stage. During the subsequent CO2 injection, the tomographical array allowed to follow the CO2 migration front inside the sediment sample and helped to identify the CO2 breakthrough.

Download or read book Gas Hydrates 2 written by Livio Ruffine and published by John Wiley & Sons. This book was released on 2018-04-16 with total page 387 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas hydrates in their natural environment and for potential industrial applications (Volume 2).

Download or read book Sediment hosted Gas Hydrates written by D. Long and published by Geological Society of London. This book was released on 2009 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is much interest in gas hydrates in relation to their potential role as an important driver for climate change and as a major new energy source; however, many questions remain, not least the size of the global hydrate budget. Much of the current uncertainty centres on how hydrates are physically stored in sediments at a range of scales. This volume details advances in our understanding of sediment-hosted hydrates, and contains papers covering a range of studies of real and artificial sediments containing both methane hydrates and CO2 hydrates. The papers include an examination of the techniques used to locate, sample and characterize hydrates from natural, methane-rich systems, so as to understand them better. Other contributions consider the nature and stability of synthetic hydrates formed in the laboratory, which in turn improve our ability to make accurate predictive models.

Download or read book Sources of Biogenic Methane to Form Marine Gas Hydrates written by and published by . This book was released on 1993 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Potential sources of biogenic methane in the Carolina Continental Rise -- Blake Ridge sediments have been examined. Two models were used to estimate the potential for biogenic methane production: (1) construction of sedimentary organic carbon budgets, and (2) depth extrapolation of modern microbial production rates. While closed-system estimates predict some gas hydrate formation, it is unlikely that>3% of the sediment volume could be filled by hydrate from methane produced in situ. Formation of greater amounts requires migration of methane from the underlying continental rise sediment prism. Methane may be recycled from below the base of the gas hydrate stability zone by gas hydrate decomposition, upward migration of the methane gas, and recrystallization of gas hydrate within the overlying stability zone. Methane bubbles may also form in the sediment column below the depth of gas hydrate stability because the methane saturation concentration of the pore fluids decreases with increasing depth. Upward migration of methane bubbles from these deeper sediments can add methane to the hydrate stability zone. From these models it appears that recycling and upward migration of methane is essential in forming significant gas hydrate concentrations. In addition, the depth distribution profiles of methane hydrate will differ if the majority of the methane has migrated upward rather than having been produced in situ.